U-Pb and Hf-isotope analyses of zircon from the Kundelungu kimberlites, D.R. Congo : implications for crustal evolution

The Gungwania and Talala kimberlitic pipes on the Kundelungu Plateau (Katanga, SE Congo) have been used as drillholes, to obtain crustal zircons for a study of crustal evolution in the region and to constrain the age of the basement and the sedimentary provenance of the Katangan Supergroup. Two hundred and twenty-nine zircon grains were analysed for U–Pb ages and Hf-isotope compositions. Juvenile Mesoarchean (~3.4–3.3 Ga) crust in the region underwent recycling during Neoarchean and Paleoproterozoic time. The Paleoproterozoic event involved little production of juvenile crust, and this Paleoproterozoic crust was recycled during Mesoproterozoic and Neoproterozoic time. Both the Mesoproterozoic and Neoproterozoic were characterised by bimodal magmatism reflecting extension, linked with the break up of Rodinia and the opening of the Katangan basin, and the development of juvenile crust. Detailed studies of the external morphology of the zircons in different age groups suggest that the basement beneath the Kundelungu region is predominantly Paleoproterozoic in age; other zircon populations may be derived from the Katangan sediments. The absence of any zircons younger than 560 Ma supports deposition of the Biano Subgroup, which hosts the kimberlites, during the Pan-African Lufilian orogeny. The Archean Congo and Zimbabwe cratons, the Paleoproterozoic Ubendian Belt (Bangweulu Block), the Paleo-to-Mesoproterozoic Irumide Belt, the Mesoproterozoic Kibaran Belt and the Choma Kalomo Block may all have contributed material to the sediments of the Katangan Supergroup.31 page(s